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Assessment of the Service Life of Materials Exposed to Frost
Published in Christer Sjöström, Durability of Building Materials and Components 7, 2018
Pure frost attack is treated in this paper. By this is meant freeze-thaw in pure water and with “pure” water in the pore system. Thus, salt scaling is not considered. Frost damage will only occur when the internal stresses in the material, occurring as a consequence of transformation of water into ice, exceeds the tensile strength of the material. In a small piece of the material, completely moisture isolated from the surroundings, the stresses at a certain freezing temperature θ will only be a function of the rate of freezing of the pore water, and of the amount of freezable water. σθ=fdwf/dtθ;wfθ where σθ [Pa] is the internal stress at temperature θ [°C], (dw f/dt)θ [m3/(m3•s)] is the rate of freezing of pore water at temperature θ, and (wf)θ [m3/m3] is the amount of freezable water.
Chloride ion penetration under two-dimensional freeze-thaw attack
Published in Jaap Bakker, Dan M. Frangopol, Klaas van Breugel, Life-Cycle of Engineering Systems, 2017
K. Hashimoto, H. Yokota, T. Taniguchi
Concrete structures and members deteriorate and their performance will be degraded during the service life. In particular, frost damage due to freeze-thaw cycles causes deterioration of concrete structures in cold regions (Shashank et al, 2008). Also, chloride from deicing agents can penetrate into concrete and accelerate the deterioration due to frost damage in a freeze-thaw environment. Consequently, corrosion of reinforcing bars occurs in concrete members (Wang et al, 2014). Moreover, it has been reported that icing on the surface of concrete leads to acceleration of frost damage, which must consider the geometric conditions of the structure such as which concrete surfaces are exposed to snow cover and thaw water with chloride ion. In particular, parts of the concrete structure which have higher potential to be deteriorated by frost damage, such as bridge piers, would have chloride ion penetration two-dimensionally from the top and side surfaces of concrete. To simulate freeze-thaw environment on the surface of concrete structures considering the real environmental exposure, which shows severe damage in cold regions as mentioned earlier, it is necessary to prepare an experimental methodology to induce two- dimensional chloride ion penetration and icing behavior on the top and the side surfaces of concrete.
Actions during service
Published in Geert De Schutter, Damage to Concrete Structures, 2017
Frost damage in concrete can easily be reduced or prevented by reducing the water/cement ratio and by adding an air-entraining agent. Both measures are typically considered in concrete standards (see also Chapter 1). Prescribed maximum water/cement ratios typically range between 0.45 and 0.50, depending on the frost risk (linked to the degree of saturation). When applying air-entraining agent, additional air content ranging from 4% to 6% is typically the goal. The air voids need to have a diameter between 100 µm and 500 µm, and the spacing factor should be smaller than 200 µm. It is to be considered that for each percent of entrained air, the compressive strength of the concrete will be reduced by about 5%.
Time-dependent reliability method for service life prediction of reinforced concrete shield metro tunnels
Published in Structure and Infrastructure Engineering, 2018
Wei Yang, Hassan Baji, Chun-Qing Li
Yuan, Li, and Li (2011) surveyed 226 tunnels with a total length of about 132 km in China using video recording and Ground Penetrating Radar (GPR) scanning. They found that the damaging effect on tunnels could be classified as structural and functional. These damage effects include crack damage, water leaking, frost damage and other icing effects, corrosion of reinforcement and degradation/reduction in strength of concrete and damage to the drainage system. According to their summary on the deterioration of surveyed tunnels, as shown in Figure 1(b), 69% of the tunnels suffered from water leaking. Crack damage (53.1%) and corrosion (49.6%) were the second and third widespread damages among the surveyed tunnels.
A micromechanical model of freeze-thaw damage in asphalt mixtures
Published in International Journal of Pavement Engineering, 2021
Lisa Lövqvist, Romain Balieu, Niki Kringos
It is well known that long-term action of moisture inside asphalt pavements weakens its structure: Erosion of mastic particles as well as moisture diffusion through the mastic towards the mastic-aggregate interfaces contributes to the deterioration (Kringos 2007). Additionally, moisture inside the air voids will expand and contract depending on the traffic, causing a pumping action subjecting the walls of the air voids to a pressure. This degradation further increases the susceptibility of the asphalt to failure during the winter when the mastic becomes more brittle and thus more prone to fracturing. Additionally, moisture still trapped inside the asphalt may add to the deterioration through the expansion occurring when it freezes to ice, a phenomenon commonly referred to as frost damage. To assess frost damage, researchers have traditionally exposed the material to different numbers of freezing –and thawing cycles, to thereafter determine the evolution, as well as the severity, of the material degradation. In this fashion, it has been established that the air void content of the asphalt mixtures increase with the number of freezing –and thawing cycles (Feng et al.2010, Xu et al.2015, Luo et al.2017, Pan et al.2017) and thus leading to a decrease in complex (Lamothe et al.2017) -and resilient modulus (Si et al.2014), fracture resistance (Fakhri and Ahmadi 2017), compressive strength (Si et al.2014), and indirect -and splitting tensile strength (Feng et al.2010, Luo et al.2017, Pan et al.2017). In addition to the number of freeze-thaw cycles, the amount of air voids in the mix has, logically, been shown to affect the damage caused by freezing and thawing.
Characterization of RCAs and their concrete using simple test methods
Published in Journal of Sustainable Cement-Based Materials, 2020
Yogiraj Sargam, Bharath Melugiri Shankaramurthy, Kejin Wang
Concrete structures such as pavements undergo many cycles of freeze-thaw (F-T) in harsh winter conditions leading to frost damage of such structures and affecting their durability. Approximately 60-70% of the volume of concrete is often occupied by the aggregates. Hence, the freeze-thaw performance of concrete is greatly controlled by the characteristics of its constituent aggregates, among other factors. The aggregate characteristics affecting its F-T performance/resistance are mineralogy, size, pore structure, absorption, and impurities [25,26]. It is also influenced significantly by the pore structure (or absorption) of the constituent aggregate, amongst other factors. The RCAs used in this study had relatively high absorption which might affect the overall F-T resistance of concrete and therefore it was required to be evaluated. There are various test methods available for this purpose such as ASTM C88, ASTM C666, CSA A23.2-24A, and others. Canadian Standards Association (CSA A23.2-24A) test method for the resistance of unconfined coarse aggregate to freezing and thawing [27], has been reported to have a better correlation with field performance than other tests [28] and therefore this test method was employed in this study. In this test, aggregate samples were kept in separate plastic containers filled with 3 percent by mass of NaCl solution, as shown in Figure 3(b). The samples were then soaked at room temperature for 24 h after which these were transferred to a freezer at -20 °C for 16 h Figure 3(c), then thawed for 8 h at room temperature. Five cycles of F-T were run after which the aggregate samples were washed with tap water and oven-dried to a constant mass. The percentage mass loss for each sample due to F-T cycles was used as a measure of relative F-T performance of RCAs.